Contact Information

• D. Capone
  
  

General Research Facilities

• Anechoic Chamber
• Drafting & Design
• High Pressure Testing
• Instrumentation
• Machining
• Modeling
• Navigation
• Tunnels

Program-Specific Facilities

• Acoustics Research
  • Acoustic Reverberant Tank
  • Acoustic Test Tank
• Computing Services
• Environmental
• Scanning Laser Vibrometry
• Materials Processing
• Pump Loop Facility
• Nuclear
• Vehicle Test Range
  

acoustic reverberant tank

The Structural Acoustics Laboratory has a fabrication facility for unsteady pressure and force instrumentation and an 8- by 8- by 25-foot tank for in-water testing. This facility produces the following measurements: calibration of model-installed acoustic pressure and unsteady force transducers, admittance and damping of large-scale structures, fiber-optic laser vibrometry of large structures, and structural radiation efficiency within reverberant nonsymmetric tank inserts. This laboratory is equipped with inverters to drive motors within test models.

Acoustic water tank facilities include complete instrumentation for measuring and calibrating transducers and transducer arrays. These instruments measure frequency-response characteristics, directivity patterns, impedance, and admittance over a frequency range of 1 kHz to 1 MHz. Electrical signals to the sound projectors and from the receiving hydrophones are pulse-gated, permitting directly transmitted sound levels to be measured before the first reflections arrive.

Acoustic absorbing materials on the tank walls reduce the reverberation level so that interference with succeeding pulses is minimized. Tank 1 specifications are:

• Tank size - 26 ft x 17.5 ft x 18 ft
• View ports - three 20-inch square windows located to accommodate holography equipment
• Lighting - three portable 1,200-watt underwater lights
• Tank opening - 26 ft x 50 in
• Crane - two-ton hoist and rail system

Reverberant Water Tank

• Tank size - 28.7 ft x 22.7 ft x 18 ft
• View ports - one bowed, three-pane window located at mid-depth to accommodate holography equipment
• Lighting -none internal, but large open area for easy viewing with overhead lighting
• Tank opening - 19.7 ft x 23.6 ft
• Crane - three-ton, two-axis hoist and two moveable bridges, one with five fixed test wells and the other with rails to accommodate a pedestal stand. In addition to the standard testing, capabilities have been developed to directly interface with sensor systems that have digital inputs.

Instrumentation: Computer-controlled data acquisition system using four-channel dynamic signal analyzer, GPIB controllable switch, and GPIB controllable filter/amplifiers. Variety of waterproof accelerometers, electromagnetic and piezoelectric shakers, force gauges, underwater sources, hydrophones and a scanning laser vibrometer (SLV). Frequency range of measurements for accelerometers and pressure transducers is 100 kHz and for SLV is 200 kHz.

Measurements Performed: Radiation efficiency, admittance, and modal analysis using accelerometers or the SLV. Mechanical loss factors and radiation loss factors using integrated impulse response techniques.

acoustic test tank

The Acoustic Test Facility, housed in the Applied Research Laboratory Building, has complete instrumentation for determining the acoustic characteristics of sonar devices. Operated by the Acoustic Systems Group, routinely made measurements include frequency response calibrations, radiation pattern plots, and impedance and admittance characterizations.

The primary test tank was constructed in 1969, measures 26 ft long x 17.5 ft wide x 18 ft deep, and is structurally isolated from its surroundings. It is lined with an absorber, Saper-T, on four sides and the bottom and has three 20 x 20 inch underwater view ports.

Two mechanical cranes on rail systems, each capable of handling two tons, can be utilized to rig transducers and arrays to an extension pedestal and to fixed placement carts for accurate positioning and synchro-controlled measurement of azimuth and depth. Water temperature is an ambient 72°F with thermoclines minimized by constant circulation and filtering of the water with a quiet pump. The PC-controlled console measurement system is based around the Hewlett-Packard 89410A vector signal analyzer, which utilizes precision time gated signal processing for accurate calibration. Well-equipped climate-controlled fabrication, assembly, and repair facilities are supplemented by a vacuum potting room with flow hood to round out the integrated transducer and array design and testing capabilities. In addition to the tank measurement system, other instrumentation on hand includes Hewlett-Packard 4194 and 4192 Impedance Analyzers with high-speed color plotters and a Saturn spectrum signal analyzer.